He also never really needed them in the OT as well. Also, Artoo was serving on the Tantive IV (as we are meant to understand) for the time between ROTS and ANH. Since he would have had no need for boosters on a ship such as that, they might have been removed by Antilles.

And come on guys, Star Wars is not the first series of films to have plot holes. Terminator, Back to the Future, Indiana Jones, etc. They do not have plot holes because Lucas is an idiot (which he is), they have plot holes simply because that's the way things happen.